SWIFTUI 和 Core Motion

Posted 2023-03-05

【中文标题】SWIFTUI 和 Core Motion

【英文标题】：SWIFTUI and Core Motion

【发布时间】：2020-05-26 10:46:59

【问题描述】：

我正在尝试在 SWIFTUI 视图中显示加速度计数据。此代码可以打印到控制台，但我不明白如何在视图中获取它，因此我可以在 SWIFTUI 中使用它。

import SwiftUI
import CoreMotion


struct AccelerometerView: View 

    let motionManager = CMMotionManager()
    let queue = OperationQueue()


    var body: some View 

        VStack
            Text("accelerate:").onAppear 
                print("ON APPEAR")
                self.motionManager.startDeviceMotionUpdates(to: self.queue)  (data: CMDeviceMotion?, error: Error?) in
                    guard let data = data else 
                        print("Error: \(error!)")
                        return
                    
                    let attitude: CMAttitude = data.attitude

                    print("pitch: \(attitude.pitch)")
                    print("yaw: \(attitude.yaw)")
                    print("roll: \(attitude.roll)")
                
            //.onappear

            //Text("Pitch:\(attitude.pitch)")

        //Vstack

    //view
//struct

struct AccelerometerView_Previews: PreviewProvider 
    static var previews: some View 
        AccelerometerView()
    

【参考方案1】：

这是可能的解决方案

struct AccelerometerView: View 

    let motionManager = CMMotionManager()
    let queue = OperationQueue()

    @State private var pitch = Double.zero
    @State private var yaw = Double.zero
    @State private var roll = Double.zero

    var body: some View 

        VStack
            Text("Pitch: \(pitch)")
            Text("Yaw: \(yaw)")
            Text("Roll: \(roll)")
        //Vstack
        .onAppear 
                print("ON APPEAR")
                self.motionManager.startDeviceMotionUpdates(to: self.queue)  (data: CMDeviceMotion?, error: Error?) in
                    guard let data = data else 
                        print("Error: \(error!)")
                        return
                    
                    let attitude: CMAttitude = data.attitude

                    print("pitch: \(attitude.pitch)")
                    print("yaw: \(attitude.yaw)")
                    print("roll: \(attitude.roll)")

                    DispatchQueue.main.async 
                        self.pitch = attitude.pitch
                        self.yaw = attitude.yaw
                        self.roll = attitude.roll
                    
                
            //.onappear
    //view
//struct

【讨论】：

行得通！你能解释一下 DispatchQueue 是如何工作的吗？非常感谢您的快速回复。

Dispatch Queue 是一个对象，用于管理应用程序主线程或后台线程上的串行或并发执行。在这种情况下，CoreMotion 的回调是一个后台线程，因此您需要在主线程中更新 vars（UI 更新总是必须在主线程中完成）